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PatchSiren cyber security CVE debrief

CVE-2026-81738 OpenVPN CVE debrief

OpenVPN 2.5.0 through 2.7.6 on Windows using the tap-windows6 driver allows attackers to trigger an out-of-bounds write via crafted DOMAIN-SEARCH entries. This CVE has a CVSS score of 2.3 and is considered LOW severity. The CVE was published on 2026-09-07T08:17:13.270Z and has not been modified since then. Defenders should prioritize verifying OpenVPN versions and configurations, especially on Windows systems using the tap-windows6 driver, to prevent potential out-of-bounds write vulnerabilities.

Vendor
OpenVPN
Product
Unknown
CVSS
LOW 2.3
CISA KEV
Not listed in stored evidence
Original CVE published
2026-09-07
Original CVE updated
2026-09-07
Advisory published
2026-09-07
Advisory updated
2026-09-07

Who should care

Defenders responsible for OpenVPN configurations and Windows systems using the tap-windows6 driver should assess exposure and verify versions.

Why it matters

Defenders should prioritize verifying OpenVPN versions and configurations, especially on Windows systems using the tap-windows6 driver, to prevent potential out-of-bounds write vulnerabilities. The CVE has a CVSS score of 2.3 and is considered LOW severity, but further verification is needed to determine the extent of the issue.

  • Verify OpenVPN versions and configurations to prevent potential out-of-bounds write vulnerabilities.
  • Monitor for crafted DOMAIN-SEARCH entries that could trigger the vulnerability.
  • Implement compensating controls to mitigate potential impacts on Windows systems using the tap-windows6 driver.

Technical summary

The vulnerability allows attackers to trigger an out-of-bounds write via crafted DOMAIN-SEARCH entries in OpenVPN 2.5.0 through 2.7.6 on Windows using the tap-windows6 driver. This vulnerability has a CVSS score of 2.3 and is considered LOW severity. Defenders should prioritize verifying OpenVPN versions and configurations, especially on Windows systems using the tap-windows6 driver, to prevent potential out-of-bounds write vulnerabilities.

Defensive priority

Defenders should prioritize verifying OpenVPN versions and configurations, especially on Windows systems using the tap-windows6 driver.

Recommended defensive actions

  • Verify OpenVPN versions and configurations on Windows systems using the tap-windows6 driver.
  • Monitor for crafted DOMAIN-SEARCH entries that could trigger the out-of-bounds write vulnerability.
  • Consider implementing compensating controls to mitigate potential impacts.

Evidence notes

The CVE record and NVD detail page provide information on the vulnerability, but further verification is needed to determine the extent of the issue. The vulnerability allows attackers to trigger an out-of-bounds write via crafted DOMAIN-SEARCH entries in OpenVPN 2.5.0 through 2.7.6 on Windows using the tap-windows6 driver. OpenVPN configurations and Windows systems using the tap-windows6 driver should be assessed for exposure and verified for versions. Compensating controls may be be

Sources and references

Verified primary and authoritative sources

  • CVE-2026-81738 CVE Program record

    Publisher, destination, and source semantics verified

    URL: https://www.cve.org/CVERecord?id=CVE-2026-81738

    CVE Program - Official CVE Program record with source-provided CVE metadata.

  • CVE-2026-81738 NVD vulnerability detail

    Publisher, destination, and source semantics verified

    URL: https://nvd.nist.gov/vuln/detail/CVE-2026-81738

    NIST National Vulnerability Database - Official NIST NVD detail page and source-specific vulnerability assessment.

Supplemental references

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.